4 month sleep regression ??

Has anyone’s baby had a major loss of appetite during this time?? My baby recently has been taking in HALF of what she typically was! She was having 24oz everyday, and now she typically has half that. I already took her to the pediatrician, and I was told not to worry. But I’ve been worrying nonstop anyway trying to figure out why this has happened! It literally just hit me that this could be why??? I’m still worrying because I swear I can tell a weight difference, and it feels like she’s losing weight, not gaining. Looking into getting a second opinion.